RICHMOND (CBS SF) — About 200 people listened Monday night to a panel of state, local and federal officials and a representative of the Chevron Richmond refinery discuss why a pipeline became corroded and breached on Aug. 6, causing a devastating fire and pollution leakage that sickened 15,000 people.

“It’s not an accident. It’s a disaster,” said Frank Cambra, a former design and study contractor for Chevron at the Richmond refinery, one of a dozen speakers who lined up in the Richmond Memorial Auditorium to vent before the panel. “It’s a pattern by Chevron to put profit motive over public safety.”

Cambra said in an interview that Chevron may have used the wrong material in its blended steel pipe, which was unable to sustain hydrogen sulfide that contaminates so-called sour crude oil the company sent through the Richmond pipeline.

Chevron should be using sweet crude, which is freer of contaminates than sour crude and causes far less corrosion in metal pipes, he said.

Chevron spokeswoman Heather Kulp said the root cause of the pipe leak was high temperature sulfidation corrosion from the fuel moving within the five-foot segment of the refinery’s eight-inch-round 200-foot-long carbon steel pipe.

That segment of the steel pipe failed due to low silicone content inside, she said. The problem is that sulfidation of the pipe may occur even when a pipe is being monitored, she added.

KCBS’ Chris Filippi Reports:

Chevron did monitor 19 different parts of the pipe, starting in November 2011. However, Kulp admitted that Chevron’s inspection had missed the five-foot section where the breach happened.

“It doesn’t appear that this was effectively recognized or understood,” Kulp said.

As part of its plan to prevent it from happening again, Chevron has installed free pollution monitors along its fence line around the Richmond refinery and is working with neighborhood councils to install three other monitoring stations in residential communities near the facility, to be completed by early next year, Kulp said.

Kulp also defended Chevron against media reports that the company deliberately rerouted pipes away from monitoring stations to prevent detection of sulfur dioxide pollution emissions.

She denied pipes were diverted and said pollution unleashed was very low, only 200 pounds over several years, a level so low the government does not require a report.

But she did apologize on behalf of the company. “We are truly sorry for what happened, we are working every day to make sure this doesn’t happen again,” she said.

The Aug. 6 fire was triggered when a pipe leaking oil fumes exploded, causing a devastating fire and a vapor plume that spread for miles and caused 15,000 people to report to hospitals complaining of breathing problems.

Steve Cutchen, investigator for the U.S. Chemical Safety Board, said the agency’s examination of the refinery fire will take about 12 to 18 months, but so far he has discovered that the metal in the pipe that leaked had corroded by 80 percent to only one-sixteenth of an inch, about the thickness of a penny.

The chemical safety board wants to see if the corrosion that caused the pipe to fail was caused by sulfur in the fuel that ran through it, and how the vapor cloud that ignited the fire was formed.

Cutchen said that while Chevron inspected the entire pipe in 2011, “there is no indication that this segment was inspected.”

“We do know that there was a considerable amount of hydrocarbons in that release,” he said. “The accident in the Chevron refinery in Richmond was a close call. It could have been far worse.”

The board plans to wrap up its examination of all parts of the pipe and release the parts back to Chevron within a few weeks, he said.

Dan Meer, an assistant director for the Environmental Protection Agency, said the EPA has scheduled an on-site audit of the refinery for next week and will review the facility’s safety culture and management system.

The California Occupational Safety and Health Administration is also investigating the Richmond refinery accident and has launched a second probe of the Chevron refinery in El Segundo, since it has a crude unit that processes fuel similar to Richmond, said Ellen Widess, the agency’s chief.

Cal-OSHA intends to see if Chevron violated state worker safety regulation and the agency has the ability to issue citations and fines for violations, Widess said.

Katherine Hern, who heads the Contra Costa County Sheriff’s Office Community Warning System, said the county is refining its telephone advisory system, which she said had suffered from glitches after the gas leak, including repeatedly ringing about 4,000 numbers without moving on to new numbers.

(Copyright 2012 by CBS San Francisco and Bay City News Service. All Rights Reserved. This material may not be published, broadcast, rewritten, or redistributed.)